Process of manufacturing gray pig iron



Oct. 6,1931. F. GREINER 1,826,211

PROCESS OFMANUFACTURING GRAY PIG IRON Filed May- 14 1928 InyenorPatented Oct. 6, 1931 UNITED STATES PATE OFFICE FRITZ GBEINER,

FABRIK ESSLINGEN, OF

ESSLINGEN, GERMANY PROCESS OF MANUFACTURING GRAY PIG IRON Application,mea may 1a, ieee, serial No.

My invention relates to al process of manufacturing gray iron castingsof any desired structure having a low percentage of carbon and is animprovement on the process described in my copending application, SerialN o. 146,801, filed November 6, 1926, now Patent No. 1,746,467.According to the process described in that application the desiredphysical properties and structure are obf tained by controlling thecomposition of the mixture from which the castings are made in such amanner that the total content of C Si is selected in accordance with thethickness of the walls of the article to be cast, the proportion ofC-l-Si being increased as the wall thickness decreases, ;tor producingany given structure. Y.

For producing an iron with a low percentage of carbon which isfrequently aimed at and especially desired at the present time, in vviewof the great tensile strength resulting therefrom and due to thedecrease of the number and size of the graphite lamellae, the methoddescribed in my said copending application does not suiiice. For thisreason in suclrcases according to my invention the percentagc of thecarbon is retained unaltered and only the amount of silicon contained inthe iron is made to suit the varying conditions. The amount of siliconrequired with regard to the wall thickness can then be ascertained in asimple manner from a diagram owing to relations which by law existbetween the wall thicknesses on the one hand and the amounts of carbonand silicon on the other hand.

Thus according to my invention the process consists therein that for.the largest possible group of compositions of varying wall thicknessesand for the percentage of carbon is maintained the same and that onlythe percentage of silicon is altered accordingly. Thisis preferably donewith reference to a diagram as shown on the drawing in which the wallthicknesses are marked on the ordinates and the contents of silicononthe absci'ssae. For a certain contents of carbon of for instance 3%the contents of siliconnecessary for a definite wall thickness can thenbe taken from 277,746, and in eeman'y nay ar, 1927..

a straight line the values of which increase as the wall thicknessesdecrease. It is then still left at the discretion of the foundrynian todecide upon the contents of carbon most favourable for the occasion. Itis usually fixed aty between 2.8 and 3%, as with such contents the ironpossesses a great 'liuxibility and also a Very high tensile strength.

I claim as my invention:

l. The process of producing a gray iron casting of any desired structurewhich consists in first preparing a molten mixture of iron, carbon andsilicon, the proportion of silicon being adjusted in accordance with acurve which rises substantially in a straight line as the wall thicknessof the article to be cast decreases, the proportion of carbon beingmaintained substantially the same for all Wall thicknesses, and thenpouring said molten mixture into a mold. I

2. The process of producing a gray iron casting of any desired structurewhich consists in first preparing' a molten mixture of iron, carbon andsilicon, the proportion ot silicon being adjusted in accordance with acurve which rises substantially in a straight line from 0.8% to 2.8% asthe wall thickness decreases from 50 mm. to 5mm., the proportion ofcarbon being maintained at 3% for all wall thicknesses, and then pouringsaid molten mixture into a mold.. y

3. The process of producing a gray iron casting of a particularstructure which consists in first preparing a molten mixture of iron,carbon and silicon, the carbon content being low and substantially thesame for a large group of wall thicknesses of the articles to be castand the silicon content being adc j usted t the wall thickness inaccordance with diierent kinds of castings the diagram shown in thedrawing, pouring the mixture into a mold.

In testimony whereof I aiiix my signature.

FRITZ GREINER.

and then

